This project will investigate the evolution of treated and untreated stroke in patients recruited from the collaborative brain stroke program of NINDS, the Clinical Center, and Suburban Hospital. The study will use anatomical and functional imaging techniques with emphasis on the acute and subacute stage (less than 1 month) of the disease. During the acute phase (less than 6 hours post-ictus) and following up at 12, 24, and 48 hours and at 2 to 4 weeks we will perform the study using various pulse sequences to define temporal relationships. From these pulse sequences, several voxel maps (and their putative significance) will be created. Magnetic resonance angiograms will be evaluated for stenosis according to the NASCET criteria for the internal carotid arteries and similar percent stenosis for other vessels. Region of interest (ROI) analysis will be performed on these maps. Analysis of variance (ANOVA) will be used to evaluate the significance of the differences among volume measurements from these parameters. Parallel to this analysis will be a normalization of results from all pulse sequences into Talairach space (Brain Atlas) while perserving tissue volumetric units (i.e., the size of the lesion). This framework allows correlation of location and intensity of the parametric information from any pulse sequence with underlying morphological information or para-metric information from any other pulse sequence as well. Signal and volumetric changes with time will also be analyzed. We will begin to enroll subjects. For the first 6 months, we will only enroll subjects who are capable of providing valid informed consent. After 6 months, we will report on our progress and experience with obtaining consent in the emergency room setting to the NINDS IRB.